碩士 / 國立中興大學 / 生命科學系所 / 106 / Understanding the evolutionary pattern and process of terrestrial species on oceanic islands are key topics in biogeography. Ocean is a critical geographical barrier for terrestrial species, especially for non-vagile species which cannot fly or swim. Pachyrhynchus weevils (Insecta: Coleoptera: Curculionidae) are flightless with fused elytra and atrophic hind wings, and the colonization history of Pachyrhynchus weevils inferred from genetic data revealed long distance dispersal to remote oceanic islands through rafting on ocean currents. Here, we used captive-breeding Pachyrhynchus jitanasaius to study (1) the physiological tolerance of weevils among different stages (egg, larva, or adult) under salinity of 0.2 (freshwater), 16.5 (brackish water), and 35 ‰ (seawater), respectively; (2) the survival rate of larva in a simulated ocean environment in laboratory; and (3) the survival rate of larva in a field-floating experiment on the Pacific Ocean along with the Kuroshio Current. In the salinity tolerance experiment of eggs, we found that the hatching rate and egg period of P. jitanasaius has no difference under the different salinity treatments. The survival rate of larva under seawater environment is lower than freshwater environment, but if larvae survived after 7 immersing days, they can emerge into adults in subsequent rearing process as other treatments. However, no adults can survive regardless of the different salinity treatments for more than 2 days. After floating 6 days in salty water, 11% larvae in the simulated environment and 9% larvae in the field-floating experiment successfully survived in the “vehicles” (fruit of Barringtonia asiatica). We provided the first empirical evidence that eggs and larvae may be the most probable mechanisms to cross the oceanic barrier, and also revealed that the larvae survive successfully rafting on ocean current. This ability may facilitate the over-sea dispersal of these wingless weevils, and further shape the distribution and speciation pattern of this highly diverse taxon on west Pacific islands.
| Identifer | oai:union.ndltd.org:TW/106NCHU5105001 |
| Date | January 2018 |
| Creators | Hui-Ying Yeh, 葉鏸瑩 |
| Contributors | 黃文山 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 32 |
Page generated in 0.0015 seconds